The invention relates to a locking device for objects of use, to be used for a restricted period of time, and a method for the controlled use of the objects of use.
Electronic access authorization systems offer, in comparison with mechanical locking systems, a much higher degree of flexibility in the individual issue and withdrawal of access authorizations.
Many different forms of such electronic access authorization systems are known which employ differing communications procedures and identification means, these includes for example cards, magnetic cards, chip cards, processor chip cards, transponders and the like, whereby the data exchange takes place via electrical contacts, electromagnetic or infrared signals and the like. Further, there are known combination locks which are operated by the entry of codes via a key pad and which employ particular protocols and algorithms for control and reprogramming.
The principle of code switching, which brings about an increase in security against improper information monitoring (bugging) is found in a series of publications such as e.g. DE 27 35 048 C2 or DE 43 25 137 A1. However, these systems are based upon the employment of intelligent keys, equipped with memories.
DE 30 31 405 and a series of similar systems, which are based upon sophisticated code conversion methods, involve storage of access authorization relationships in the lock or in a key.
With all such systems it is disadvantageous that the checking of the access authorization of the user takes place directly and locally in the lock itself, so that the access authorization information must be stored in the lock and/or in the key. This brings about the following problems:
The loss of a key means that there is a risk of misuse for all locks which the key fits. In the case of loss, these locks must all be so reprogrammed, at their locations, that the lost key is in future rejected.
The same applies to key-less systems which work only with the input of codes via a keyboard, in the case that a code becomes known or is detected by improper monitoring (bugging).
It is further disadvantageous that the programmed access authorization relationship can be checked or changed only with difficulty, because all locks concerned and/or keys must be checked and reprogrammed. The effort involved thus increases rapidly with increasing complexity of the access authorization relationship between users or keys or codes and locks, and requires a high level of organisation.
In DE 20 58 623 there is described a device which overcomes the above-mentioned disadvantages in that the access relationship is administered in a central access control unit, whereby, however, a cabling the locks with the access control unit is necessary, which is of disadvantageous.
In DE 24 01 602 C2, which is most closely related to the invention set out here and which likewise employs a central code issuing device and decentral locking devices, the significant disadvantage of a need for cabling is removed. There is described a method for the alteration of lock combinations specifically for use in hotels, which is based upon the fact that the end code of a cycle n is the same as the opening code of the cycle n+1, so that the first input of a new code deactivates the old code.
With regard to employment in a hire system, it is however disadvantageous with this system that the end of the cycle of use cannot be determined by the current user but only occurs with the beginning of the next cycle of use; that is, is initiated by the next user. This means, inter alia, that the current user cannot prove that his current cycle of use has ended. This, however, excludes employment in a hire system. It is further disadvantageous with this system that problems can appear when the code issuing unit and a locking device "get out of step"; that is, are no longer synchronized.
In DE 43 01 039 C2 there is described a method for the release of vehicles for a particular user, dependent upon a reservation. This, however, requires high technical outlay (cordless telephone) in relation to the object of the use, and fixed parking places in the vicinity of hire stations.